petersen



Jan. 9, 1962 GA. PETERSEN SCREW. ANCHOR 2 Sheets-Sheet 1 Filed Jan. 16, 1959 INVENTOR Gerald A. Petersen Jan. 9, 1962 G. A. PETERSEN 3,016,117

SCREW ANCHOR 2 Sheets-Sheet 2 Filed Jan. 16, 1959 Fig 3. INVENTOR 3| Gerald A. Petersen i i I m United States Patent ice 9,

drawings but it will be understood that other shapes, 3,016,117 preferably non-circular, may be employed. Sockets 15 SCREW ANCHOR v Gerald A. Petersen, Saratega, Calif. Petersen Engineering Co., 461 Kifer Road, Santa Clara, Calif.)

Filed Jan. 16, 1959, Ser.'N0.',787,198 Claims. (Cl. 189-91) This invention relates'to a new and improved screw anchor in which the blade of the screw has a particular shape which enables the anchor to be used under condiand 15amay be continuous if the shank 16-and shaft 11 are of the same cross-section. Pin 18 passes throughhub 13 of shank'16 to secure the two parts together. Collar 19' on shank 16'provides a stop for hub '13. Below collar" 19 the lug is flat as indicated by reference .numeral 2l.

tions not feasible-with ordinary screw anchors. The purpose of screw anchors is to function as a stationary support in the ground for an anchor rod for guy wires and the like. The anchor has an anger type blade which is rotated either manually or by machine to force its way into the ground to provide the necessary stationary support.

The present anchor has a blade constructed in such manner that it may be used in ordinary ground or ground containing small rocks. The anchor may also be used in locations where the soil is sand or mud. Ordinary screw anchors cannot be screwed into firm or ordinary earth, but onlyinto sand, very loose earth, mud, or the like. p

' A feature of the invention is the fact that the blade has a curved cutting edge of decreasing angularity which enables the anchor to slice through the soil. Because of the decreasing angularity, the entire cutting edge of the blade functions to slice through the ground continuously simultaneously and this enables the anchor to "be used under conditions where conventional anchors cannotbe employed. p

The blade construction has the additional advantage of turning through the soil more easily which reduces power requirements. v

Still another feature of the invention is the fact that the tendency of the shaft to break off at the attachment lug is reduced because the blade turns more easily.

Another feature of the invention is provision of a pivotally mounted plate on the trailing edge of the blade which is normally parallel to the blade and inoperative. However, when the anchor is turned in a reverse direction the plate is pushed down to vertical position by the dirt acting upon it and thus arrests such reverse rotation.

Other objects of the present invention will become apparent upon reading the. following specification and referring to the accompanying drawings in which similar characters of reference represent corresponding parts in each of the several views.

In the drawings:

FIG. 1 is a side elevational view of the anchor including the lower portion of the shaft partly broken away in section.

FIG. 2 is a top plan view as taken substantially along the line 22 of FIG. 1. 7

FIG. 3 is a sectional view of the cutting edge taken substantially along the line 33 of FIG. 2.

FIG. 4 is a schematic bottom plan view showing the development of the curvature of the cutting edge.

FIG. 5 is a fragmentary sectional view taken substantially along line 55 of FIG. 2.

The screw anchor is mounted on the lower end of shaft 11, here shown as square. It will be understood that shafts of other cross-sectional shape may be employed although preferably, the shaft should be non-circular. On the lower end of shaft 11 is located the anchor blade 12 which has an elongated hub 13 having an upper socket to receive shaft 11. Pin 14 passes through the upper end of hub 13 and through a suitable hole in shaft 11 to secure the two parts together. The lower end of the hub 13 has a lower socket 15a to receive the upper shank 16 of drive lug 17. Lug 17 is described in Patent No. 2,863,640.

Below the lug 17 is a fish tail type pilot bit 22 formed with socket 23 in its upper end to receive the lOWCIf'EIld of the flattened portion 21. A pin 24 passes through'the upper end'of bit 22to secure the same to lug 17. The

shape of pilot bit 22 is best shown in FIG. 1 and is de- Shank 16 is likewise shown square in the accompanying I scribed in Patent No. 2,773,673. A pair of'blades 26 are employed which project out from the body of the bit in a downwardly inwardly helically curved direction and merge at their upper ends with the body of the bit.

The shape of blade 12 is an important feature of the invention. The body of the blade is a relatively thin helix having a slight'pitch. The shape of the blade illustrated is for clockwise rotation'of-shaft 11, as viewed in FIG. 2.

' An optional feature of'the device is theuse of a rectangular, radiallypositioned stop plate 61 on the trailing edge 48 of the blade. To mount plate 61, hinge lugs 62 are formed on blade 12 and corresponding lugs 63 on plate 61 pivotally interconnected by removable pins 64. Lugs 62 are formed withdownward projecting stops 66 which restrain pivotal movement of plate 61 beyonda vertical position. In ordinary use of the anchor, plate 61 extends parallel to *the blade. If, by mistake, a reverserotation is attempted, plate 61 ispushed down to'vertical position by the dirt acting upon it and stops such motion.

' For purpose of development of shape of cutting edge 31 "it may be assumed that the blade commences at a point 34 spaced outwardly from the center 35 of the shaft 11 a distance equal to the outside radius of pilot bit 22. (See FIG. 4.) From center 36 a series of concentriccircles, 38, a, b, c, and d, is struck, each circle having a radius one-eighth inch 0A3) greater than the next circle. Circle 38a passes'through point 34. At point 34 a tangent line 39 is erected. Reference line 41 is positioned at an angle of 25 from tangent line 39. Point 42b on the cutting edge 31 is located at the intersection of reference line 41 and concentric circle 38b.

Point-42c is located in the following manner: Tangent line 320 is erected at point 42b. A reference line 410 is located at an angle of 24 with respect to tangent line 390 and intersects circle 380 at point 42c.

Similarly, each succeeding point 42d on the cutting edge is established with decreasing angles in decrements of 1 with the tangent at the preceding point. This shape is carried around to point 46 which is located from center 36 a distance equal to the maximum diameter of the blade. From point 46 to point 47 the outside diameter of blade 12 is uniform. At point 47 the blade ter minates in a radial terminal edge 48. (FIG. 2.)

The cross-section of the blade is shown in FIG. 3. The top surface 51 is relatively flat. The portion 52 at the outer edge immediately below the top surface is beveled at an angle of about 30 and inside the beveled portion 52 the bottom edge 53 is substantially parallel to the top surface 51.

In use,'the shaft 11 is held disposed at the desired angle with respect to the horizontal, parallel to the guy 'wire which is to be strung and is turned either manually ground where conventional screw anchors cannot be used as well as in sand, very loose earth, mud, or the like, where conventional screw anchors may be used. When the shaft 11 is buried to the desired depth, the turning equipment is removed and the guy wire attached in a manner well understood in this art, The stop plate 61 prevents reverse rotation of the shaft.

Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it is understood that certain changes and modifications may be practiced within the spirit of the invention and scope of the appended claims.

What is claimed: 1,

1. A screw anchor comprising a shaft, a hub on said shaft, and a helical blade on said hub, said blade have a cutting edge having a curved configuration connecting a series of points, said points being situated on concentric circles of radii increasing in equal increments, the first point being located on the innermost of said circles at a radius slightly greater than that of said hub, the second point being located at the intersection of the second innermost of said circles with a first line drawn at a predetermined'first angle with a tangent to said first point, the third point being located at the intersection of the third innermost of said circles with a second line drawn at a second ,angle with a tangent to said second point, said second angle at a predetermined decrement relative to said first angle, and each successive point being located at the intersections of successive circles'and lines drawn at angles diminishing at the same predetermined decrement with tangents to the preceding points, the shape of said cutting edge being such that all points along said cutting edge cut evenly, uniformly and simultaneously as said anchor is rotated in the soil.

2. An anchor according to claim 1 in which'said terminus has a substantially radial edge and which further comprises a stop plate and means mounting said stop plate extending along the length of said radial edge for pivotal movement between a position parallel to and extending away from said blade and a position substantially perpendicular to said blade.

3. A screw for a screw anchor comprising a hub and a helical blade wrapped at least partially around said hub, said blade have a cutting edge having a curved configurathe third innermost of said circles with a second line drawn at a second anglerwith a tangent to said second point, said second angle at a predetermined decrement relative to said first angle, and each successive point being located at the intersections of successive circles and lines drawn at angles diminishing at the'same predetermined decrement with tangents to the preceding points, the shape of said cutting edge being such that all points along said cutting edge out evenly, uniformly and simultaneously as said screw is rotated in the soil.

4. A screw anchor comprising a shaft, a hub on said shaft, a helical blade on said hub, said blade having a substantially radial terminal edge, a stop plate, and means mounting said stop plate extending along the length of said radial edge in a substantially radial direction for pivotal movement between a position parallel to and extending away from said blade and a positionsubstantially perpendicular to said blade.

5. A screw anchor comprising a shaft, a hub on said shaft, a helical blade on said hub, a pilot bit below said blade and adapter means connecting said bit to said hub, said blade having a substantially radial terminal-edge,'a stop plate, and means mounting said stop plate extending along the length of said radial edge in a substantially radial direction for pivotal movement between a position parallel to and extending away from said blade and a position substantially perpendicular to said blade.

References Cited in the file of this patent UNITED STATES PATENTS 756,640 Irons Apr. 5, 1904 818,061 Toy Apr. 17, 1906 1,283,246 Maloney a. Oct. 29, 1918 2,863,640 Peterson Dec. 9, 1958 FOREIGN PATENTS 1,154,394 France Oct. 28, 19 5'1 

